R trends in 2015

Author: Hadley

library("xml2")
txt <- 
"<foo> 
  <bar> text <baz/> 
  </bar>
</foo>"
x <- read_xml(txt)
x

{xml_document}
<foo>
[1] <bar> text <baz/> \n  </bar>

xml_children(x)

{xml_nodeset (1)}
[1] <bar> text <baz/> \n  </bar>

xml_find_all(x, "//baz")

{xml_nodeset (1)}
[1] <baz/>

Author: Iannone, Sveidqvist, Bostock, Pettitt, Daines, Kashcha, Iannone

library(DiagrammeR)
DiagrammeR("
  graph LR
    A-->B
    A-->C
    C-->E
    B-->D
    C-->D
    D-->F
    E-->F
", height = 200, width = 400)

library(dplyr)
library(magrittr)
data_a <- 
  data.frame(id = 1:3,
             var1 = LETTERS[1:3])
data_b <- 
  data.frame(id = 1:3+2,
             var2 = LETTERS[1:3+2])

data_a %>% 
  left_join(data_b) %>% 
  knitr::kable()

data_a %>% 
  inner_join(data_b) %>% 
  knitr::kable()

data_a %>% 
  right_join(data_b) %>% 
  knitr::kable()

data_a %>% 
  anti_join(data_b) %>% 
  knitr::kable()

data_b %>% 
  anti_join(data_a) %>% 
  knitr::kable()

set.seed(98213)
data_c <- 
  data.frame(id = c(1,1,2,2,3),
            var1 = runif(5))
knitr::kable(data_c)

data_c %>% 
  group_by(id) %>% 
  filter(var1 == min(var1)) %>% 
  knitr::kable()

# The do allows us to do custom operations
data_c %>% 
  group_by(id) %>% 
  do({
    if(nrow(.) == 1)
      return(.)
    .$var1 = min(.$var1) +
      max(.$var1)^2
    return(.[1,])
  }) %>% 
  knitr::kable()

library(multidplyr)
data_d <- 
  data.frame(id = sample(1:10, size = 10^4, replace = TRUE),
             var1 = runif(10^4))
data_d %>% 
  partition(id) %>% 
  do({
    if(nrow(.) == 1)
      return(.)
    .$var1 = min(.$var1) + 
      max(.$var1)^2
    return(.[1,])
  }) %>% 
  collect() %>% 
  arrange(id) %>% 
  tail(3) %>% 
  knitr::kable()